selftests/bpf: Test that module can't be unloaded with attached trampoline

Adding test to verify that once we attach module's trampoline,
the module can't be unloaded.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210414195147.1624932-7-jolsa@kernel.org

diff --git a/tools/testing/selftests/bpf/prog_tests/module_attach.c b/tools/testing/selftests/bpf/prog_tests/module_attach.c
index 5bc53d53d86e31e13a5346dd65d13f9ae44e130e..d85a69b7ce44912c421dcff9a6ae4e09aeaeb915 100644 (file)
--- a/tools/testing/selftests/bpf/prog_tests/module_attach.c
+++ b/tools/testing/selftests/bpf/prog_tests/module_attach.c
@@ -45,12 +45,18 @@ static int trigger_module_test_write(int write_sz)
        return 0;
 }
 
+static int delete_module(const char *name, int flags)
+{
+       return syscall(__NR_delete_module, name, flags);
+}
+
 void test_module_attach(void)
 {
        const int READ_SZ = 456;
        const int WRITE_SZ = 457;
        struct test_module_attach* skel;
        struct test_module_attach__bss *bss;
+       struct bpf_link *link;
        int err;
 
        skel = test_module_attach__open();
@@ -84,6 +90,23 @@ void test_module_attach(void)
        ASSERT_EQ(bss->fexit_ret, -EIO, "fexit_tet");
        ASSERT_EQ(bss->fmod_ret_read_sz, READ_SZ, "fmod_ret");
 
+       test_module_attach__detach(skel);
+
+       /* attach fentry/fexit and make sure it get's module reference */
+       link = bpf_program__attach(skel->progs.handle_fentry);
+       if (!ASSERT_OK_PTR(link, "attach_fentry"))
+               goto cleanup;
+
+       ASSERT_ERR(delete_module("bpf_testmod", 0), "delete_module");
+       bpf_link__destroy(link);
+
+       link = bpf_program__attach(skel->progs.handle_fexit);
+       if (!ASSERT_OK_PTR(link, "attach_fexit"))
+               goto cleanup;
+
+       ASSERT_ERR(delete_module("bpf_testmod", 0), "delete_module");
+       bpf_link__destroy(link);
+
 cleanup:
        test_module_attach__destroy(skel);
 }